U.S. patent number 7,635,107 [Application Number 11/200,515] was granted by the patent office on 2009-12-22 for system for aerodynamic flows and associated method.
This patent grant is currently assigned to The Boeing Company. Invention is credited to Roger W. Clark, David J. Manley, Arvin Shmilovich, Yoram Yadlin.
United States Patent |
7,635,107 |
Shmilovich , et al. |
December 22, 2009 |
**Please see images for:
( Certificate of Correction ) ** |
System for aerodynamic flows and associated method
Abstract
A system and method for controlling boundary layer flow over an
aircraft wing are provided. The system includes at least one wing
element, and a plurality of ports defined in the wing element and
in fluid communication with one another. The system also includes
at least one fluidic device operable to continuously ingest the
fluid through at least one of the ports and eject the fluid out of
at least one other port to control boundary layer flow of the fluid
over the wing element.
Inventors: |
Shmilovich; Arvin (Huntington
Beach, CA), Yadlin; Yoram (Irvine, CA), Clark; Roger
W. (Huntington Beach, CA), Manley; David J. (Huntington
Beach, CA) |
Assignee: |
The Boeing Company (Chicago,
IL)
|
Family
ID: |
37507310 |
Appl.
No.: |
11/200,515 |
Filed: |
August 9, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070034746 A1 |
Feb 15, 2007 |
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Current U.S.
Class: |
244/207;
244/208 |
Current CPC
Class: |
B64C
21/04 (20130101); B64C 21/02 (20130101); B64C
9/16 (20130101); B64C 9/22 (20130101); B64C
2230/06 (20130101); B64C 2230/04 (20130101); Y02T
50/166 (20130101); Y02T 50/32 (20130101); Y02T
50/10 (20130101); Y02T 50/30 (20130101) |
Current International
Class: |
B64C
21/04 (20060101) |
Field of
Search: |
;244/207,208,209,204 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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584 585 |
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Sep 1933 |
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DE |
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699 066 |
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Nov 1940 |
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DE |
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197 47 308 |
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Jul 1999 |
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DE |
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0 052 242 |
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May 1982 |
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EP |
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Other References
PCT Notification of Transmittal of the International Search Report
and the Written Opinion of The International Searching Authority,
or the Declaration, mailed Feb. 9, 2007 for PCT/US2006/029134
(Filed Jul. 26, 2006). cited by other.
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Primary Examiner: Eldred; J. Woodrow
Attorney, Agent or Firm: Alston & Bird LLP
Claims
That which is claimed:
1. A system for controlling boundary layer flow over an aircraft
wing comprising: a plurality of wing elements, wherein the
plurality of wing elements comprise a slat and a flap
interconnected to a main wing element; a plurality of ports defined
in the slat, flap, and main wing element, at least a pair of ports
in the slat, flap, and main wing element in fluid communication
with one another; and at least one fluidic device operable to
continuously ingest the fluid through at least one of the ports and
eject the fluid out of at least one other port to control boundary
layer flow of the fluid over the slat, flap, and main wing
element.
2. The system according to claim 1, wherein at least one fluidic
device comprises an electrically powered pump.
3. The system according to claim 1, wherein at least one fluidic
device employs zero net mass flow to regulate fluid flow through
the ports.
4. The system according to claim 1, wherein at least one fluidic
device is operable to actuate a plurality of ports such that fluid
flows through each of the actuated ports simultaneously.
5. The system according to claim 1, wherein at least one fluidic
device is operable to actuate a plurality of ports automatically or
manually.
6. The system according to claim 1, wherein at least one fluidic
device actuates a plurality of ports associated with at least one
of the slat, main wing element, or flap.
7. The system according to claim 1, wherein at least one port is
defined in an upper surface of at least one of the wing
elements.
8. The system according to claim 1, wherein at least one port is
defined in a lower surface of at least one of the wing
elements.
9. The system according to claim 1, wherein at least one port
defined in an upper surface of at least one of the wing elements is
in fluid communication with at least one port defined in a lower
surface of at least one of the wing elements.
10. The system according to claim 1, wherein at least one port is
defined in an aft portion of at least one of the wing elements.
11. A method for controlling boundary layer flow of a fluid over an
aircraft wing comprising: initiating fluid flow over an aircraft
wing comprising a plurality of wing elements, wherein the plurality
of wing elements comprise a slat and a flap interconnected to a
main wing element; and continuously regulating fluid flow over the
aircraft wing by ingesting and ejecting fluid through a plurality
of ports defined in the slat, flap, and main wine element to
control boundary layer flow of the fluid over the slat, flap, and
main wing element.
12. The method according to claim 11, wherein initiating comprises
initiating take-off or landing of the aircraft.
13. The method according to claim 11, wherein regulating comprises
actuating a fluidic device associated with a plurality of ports in
fluid communication with one another.
14. The method according to claim 11, wherein regulating comprises
regulating a plurality of ports simultaneously.
15. The method according to claim 11, wherein regulating comprises
ingesting and ejecting the fluid through a pair of ports defined in
an upper surface of at least one of the wing elements.
16. The method according to claim 11, wherein regulating comprises
ingesting the fluid through a port defined in a lower surface of at
least one of the wing elements and ejecting the fluid through a
port defined in an upper surface of at least one of the wing
elements.
17. The method according to claim 11, wherein regulating comprises
ingesting the fluid through a port defined in an upper surface of
at least one of the wing elements and ejecting the fluid through a
port defined in a lower surface of at least one of the wing
elements.
18. The method according to claim 11, wherein regulating comprises
ingesting and ejecting the fluid through a plurality of ports
defined in each of the plurality of wing elements.
Description
BACKGROUND OF THE INVENTION
1.) Field of the Invention
The present invention relates to a system for aerodynamic flows
and, more particularly, to a system capable of controlling boundary
layer flow over an aircraft wing.
2.) Description of Related Art
One of the design objectives of the aircraft designer is to ensure
high aerodynamic performance over a range of flight conditions. The
performance during take-off and landing is a principal design
objective of transport aircraft where high-lift capability is a key
requirement. Take-off and landing are especially challenging since
the flows are dominated by viscous effects, which are the major
determinant of aerodynamic performance, and the ability to alter
the characteristics of the viscous flow is vital to the development
of efficient high lift systems.
Techniques for altering the viscous flow structures are highly
desirable due to the great potential for improved efficiency. A
variety of fluidic actuators for manipulating viscous flows have
been developed for a wide range of applications. These actuators
provide oscillatory ejection and ingestion of fluid at various
points on the wing surface. The great appeal of these devices is
that they employ Zero-Net-Mass-Flow pulsation ("ZNMF"), i.e., no
fluidic source is needed. The advantage of ZNMF is twofold: a high
pressure container or bleed air from the engines (bleed reduces
propulsion efficiency) is avoided, and a flow control system may be
integrated without the need for complex plumbing.
Flow control systems that use oscillatory forcing may employ
electrically driven fluidics or combustion powered devices. An
electrical actuator uses a moving diaphragm or a piston to generate
blowing/suction through an orifice, while a combustion actuator
emits pulsed jets through an outlet. Generally, there are several
types of electrical actuators: electromagnetic (or voice coil, like
those used in speakers), electromechanical (piston driven), and
piezo-electric (whereby a metallized diaphragm flexes when
subjected to an electrical pulse).
For example, U.S. Pat. No. 5,988,522 to Glezer et al. discloses
synthetic jet actuators for modifying the direction of fluid flow.
The actuator includes a housing having an internal chamber, where a
mechanism in the housing is utilized to periodically change the
volume within the internal chamber so that a series of fluid
vortices are generated and projected into an external environment
out of the orifice. The mechanism may include a piston or diaphragm
that is actuated by an electrical bias or piezoelectric element.
The mechanism uses the working fluid where the actuator is being
deployed such that linear momentum is transferred to the flow
system without net mass injection into the system. In addition, a
control system is utilized to oscillate the diaphragm so that a
synthetic jet stream is propagated from the orifice.
Oscillatory fluidic actuators have proven quite effective for a
variety of flow problems. However, several shortcomings associated
with unsteady excitation must be solved before this technology is
implemented into new flight worthy air vehicles. For example,
oscillatory actuators are still in developmental stages, and their
practicality and robustness require investigation for a realistic
operational environment. In addition, pulsed excitation results in
unsteady forces and moments with significant amplitudes, which is
detrimental to structural integrity and has serious implications to
structural fatigue. This is a particularly acute problem for a
multi-element wing system where the slat and flap elements are
deployed using systems of extendible linkages and tracks. The
quality of boundary layer control due to unsteady force and moment
excitation is also limited with oscillatory actuators. Furthermore,
physical limitation of electrically driven actuators (diaphragm
displacement, size of the orifice, and the size of the chamber)
pose a limit on the maximum jet velocity and, thus, energy output.
Combustion actuators produce higher jet velocity, but their energy
output is also limited because of their small orifice. Although no
air sources are required for combustion-powered actuators, these
devices use combustible material that requires storage, supply
lines, and firewalls within the airframe. Moreover, the potential
hazard of combustion-based systems poses a major obstacle to market
acceptance by aircraft operators and the general public.
It would therefore be advantageous to provide a system for
controlling boundary layer flow over an aircraft wing. In addition,
it would be advantageous to provide a system that improves
aerodynamic performance of an aircraft wing. Moreover, it would be
advantageous to provide a system that is easily employed with an
aircraft wing for improving performance of an aircraft during
take-off and landing.
BRIEF SUMMARY OF THE INVENTION
Embodiments of the present invention address the above needs and
achieve other advantages by providing a system for controlling
boundary layer flow over an aircraft wing. The system employs
fluidic devices to regulate fluid flow through ports that are in
fluid communication with one another. As such, the ports and
fluidic devices may be located in various locations on the
multi-element aircraft wing to continuously control the boundary
layer flow over the wing and reduce viscous effects. Results of
computational fluid dynamics have shown that continuously
regulating a plurality of linked ports results in more streamlined
flow with higher circulation and reduced viscous effects. The
aerodynamic improvement produces higher lift coefficient C.sub.L
and reduced drag coefficient C.sub.D. Lift levels close to, and
higher than, inviscid levels are achievable with this flow
actuation.
In one embodiment of the present invention, a system for
controlling boundary layer flow over an aircraft wing is provided.
The system includes at least one wing element, and a plurality of
ports defined in the wing element and in fluid communication with
one another. The ports may be defined on an upper and/or lower
surface of the wing element. In addition, at least one port may be
defined in an aft portion of the wing element. The system also
includes at least one fluidic device (e.g., an electrically powered
pump) operable to continuously ingest the fluid through at least
one of the ports and eject the fluid out of at least one other port
to control boundary layer flow of the fluid over the wing
element.
In various aspects of the present invention, the fluidic device
employs zero net mass flow to regulate fluid flow through the
ports. The fluidic device may be operable to actuate a plurality of
ports such that fluid flows through each of the actuated ports
simultaneously, as well as actuate a plurality of ports
automatically or manually. The wing element may include a slat and
a flap interconnected to a main wing element. The fluidic device
may actuate a plurality of ports associated with the slat, main
wing element, and/or flap.
Embodiments of the present invention also provide a method for
controlling boundary layer flow of a fluid over an aircraft wing.
The method includes initiating fluid flow over an aircraft wing
comprising at least one wing element, and continuously regulating
fluid flow over the aircraft wing by ingesting and ejecting fluid
through a plurality of ports defined in each wing element to
control boundary layer flow of the fluid over the wing element.
Initiating fluid flow could include commencing take-off or landing
of the aircraft such that the onset of flow over the wing element
is initiated.
In aspects of the method, the regulating step includes actuating a
fluidic device associated with a plurality of ports that are in
fluid communication with one another. The regulating step could
also include regulating a plurality of ports simultaneously, and/or
ingesting and ejecting the fluid through a pair of ports defined in
an upper surface of the wing element. Similarly, the regulating
step could include ingesting the fluid through a port defined in a
lower surface of the wing element and ejecting the fluid through a
port defined in an upper surface of the wing element. Furthermore,
the regulating step may include ingesting the fluid through a port
defined in an upper surface of the wing element and ejecting the
fluid through a port defined in a lower surface of the wing
element. The regulating step could include ingesting and ejecting
fluid through a plurality of ports defined in a plurality of wing
elements, such as a slat, main wing element, and a flap.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
Having thus described the invention in general terms, reference
will now be made to the accompanying drawings, which are not
necessarily drawn to scale, and wherein:
FIG. 1 is a cross-sectional view of a multi-element aircraft wing
according to one embodiment of the present invention;
FIG. 2 is a cross-sectional view of a multi-element aircraft wing
according to another embodiment of the present invention;
FIG. 3 is a cross-sectional view of a multi-element aircraft wing
according to another embodiment of the present invention;
FIG. 4 is a cross-sectional view of a multi-element aircraft wing
according to another embodiment of the present invention;
FIG. 5A is a cross-sectional view of a multi-element aircraft wing
according to another embodiment of the present invention;
FIGS. 5B-5C are graphical images depicting various aerodynamic
properties of the multi-element aircraft wing shown in FIG. 5A;
FIGS. 6A-6C are graphical images illustrating coefficient of lift
versus angle of attack for various flap deflections for takeoff and
landing of multi-element aircraft wings according to one embodiment
of the present invention;
FIG. 7A is an image illustrating a total pressure field over a
baseline multi-element aircraft wing without flow actuation;
FIG. 7B is an image illustrating a total pressure field over a
multi-element aircraft wing according to one embodiment of the
present invention;
FIG. 8A is an image illustrating a streamwise velocity field over a
baseline multi-element aircraft wing;
FIG. 8B is an image illustrating a streamwise velocity field over a
multi-element aircraft wing according to one embodiment of the
present invention;
FIG. 9A is a cross-sectional view of a multi-element aircraft wing
according to another embodiment of the present invention;
FIGS. 9B-9D are graphical images depicting various aerodynamic
properties of the multi-element aircraft wing shown in FIG. 9A;
FIG. 10 is a graphical image illustrating a coefficient of lift
versus an angle of attack for various flow actuation modes of a
multi-element aircraft wing according to one embodiment of the
present invention;
FIG. 11A is an image illustrating a total pressure field over a
baseline multi-element aircraft wing;
FIG. 11B is an image illustrating a total pressure field over a
multi-element aircraft wing according to another embodiment of the
present invention; and
FIGS. 12A-12C are additional images depicting the total pressure
field shown in FIGS. 11A-11B.
DETAILED DESCRIPTION OF THE INVENTION
The present invention now will be described more fully hereinafter
with reference to the accompanying drawings, in which some, but not
all embodiments of the invention are shown. Indeed, this invention
may be embodied in many different forms and should not be construed
as limited to the embodiments set forth herein; rather, these
embodiments are provided so that this disclosure will satisfy
applicable legal requirements. Like numbers refer to like elements
throughout.
Referring now to the drawings and, in particular to FIG. 1, there
is shown a system for controlling the boundary layer flow over a
multi-element aircraft wing 10. The aircraft wing 10 generally
includes a plurality of wing elements 12, 14, and 16. Each of the
wing elements 12, 14, and 16 includes a plurality of ports defined
therein. Fluidic devices 18 are utilized to regulate the flow of
fluid into and out of the ports to control boundary layer flow over
each of the wing elements 12, 14, and 16. Generally, the fluidic
devices are selectively operable to control the fluid flow through
the ports during take-off and landing to improve the performance of
the aircraft wing 10. As such, the aerodynamic properties, and
particularly lift, of the aircraft wing 10 may be improved over a
range of angles of attack and under various flight conditions.
The multi-element aircraft wing 10, or airfoil, typically includes
a plurality of wing elements, namely, a slat 12, a main wing
element 14, and a flap 16. Moreover, each of the slat 12, main wing
element 14, and flap 16 includes one or more ports for controlling
the boundary layer along the surface of the multi-element wing 10.
For an exemplary description of multi-element aircraft wings and
ports defined therein, see U.S. patent application Ser. No.
11/200,506, entitled "Lift Augmentation System and Associated
Method," filed concurrently herewith, which is assigned to the
present assignee and incorporated herein by reference. However,
although reference is made herein to a multi-element aircraft wing,
it is understood that in additional embodiments of the present
invention, an aircraft wing including a single wing element may be
employed if desired. Furthermore, it is understood that flow may be
regulated by a plurality of ports and fluidic devices over any
number of lifting surfaces in order to improve aerodynamic
performance. For example, ports may be defined in a tail, rudder,
fuselage body, helicopter blade, or other aerodynamic body.
FIG. 1 illustrates a multi-element aircraft wing having a slat 12
that includes a pair of ports s1 and s2, a main wing element 14
that includes a pair of ports m2, and m3, and a flap 16 that
includes a pair of ports f1 and f2. Each of the ports is defined in
an upper surface of a respective slat 12, main wing element 14, and
flap 16. However, as shown in FIG. 2, the ports could be defined on
both the upper and lower surfaces of the aircraft wing 10 at
various positions on the aircraft wing. Thus, ports s3-s4, m4-m5,
and f6 are defined in a lower surface of a respective wing element.
The ports are generally defined to extend into a respective slat
12, main wing element 14, or flap 16 such that fluid may be
ingested or ejected through the ports. Moreover, pairs of ports
defined in a respective slat 12, main wing element 14, and flap 16
may be interconnected and in fluid communication with one another
such that one port may facilitate fluid flow into the port, while a
second port facilitates flow out of the port. However, there may be
various numbers of ports in fluid communication with one another.
For instance, referring to FIG. 2 one port f6 defined on a lower
surface of the flap 16 may be in fluid communication with a pair of
ports f1-f2 defined on an upper surface of the flap. Typically the
ports s1-s2 and m2-m3 are defined in an aft portion of respective
slat 12 and main wing element 14, however, the ports could be
defined in various wing elements and at various locations on the
slat, main wing element, or flap 16 to achieve desired aerodynamic
properties. For example, ports could be defined proximate to a
leading edge of the main wing element 14 or in one or more of the
slat 12, main wing element, and flap 16. Furthermore, although
cross-sectional views of the multi-element aircraft wing 10 are
shown, it is understood that ports may be defined in various
spanwise configurations along the wing (e.g., aligned, staggered,
non-aligned, etc.).
FIGS. 3 and 4 depict further aspects of the present invention,
wherein a Kruger slat 22 is employed. FIG. 3 shows that the Krueger
slat 22 includes ports s1 and s2, the main wing element 24 includes
ports m1 and m2, and the flap 26 includes ports f1, f2, f3, and f4.
Each of the ports shown in FIG. 3 is defined in an upper surface of
the multi-element aircraft wing 20. FIG. 4 demonstrates that ports
may be defined in both the upper and lower surfaces of the aircraft
wing 20. As such, the Krueger slat 22 includes ports s1-s2 defined
in an upper surface of the slat, while ports s3-s4 are defined in a
lower surface of the slat. Similarly, the main wing element 24
includes upper m1-m4 and lower m5-m8 ports, while the flap 26
includes upper f1-f5 and lower f6-f10 ports. Therefore, there may
be various configurations of aircraft wings and linked ports
defined in the aircraft wing to achieve desired aerodynamic
properties.
A plurality of fluidic devices 18 are employed to regulate fluid
flow into or out of the ports. The fluidic devices 18 typically
employ zero net mass flow (i.e., no external fluid source is
required) to regulate fluid flow through the ports and may use
various types of mechanisms to actuate one or more ports.
Typically, an electrically powered pump is employed to continuously
ingest (i.e., suck) and eject (i.e., blow) fluid through at least a
pair of ports that are in fluid communication with one another to
affect the boundary layer flow over a multi-element aircraft wing.
However, other constant flow devices may be used if desired, for
ingesting and ejecting fluid through the ports. Additionally,
several ports may be actuated simultaneously.
Moreover, the fluidic devices 18 are capable of actuating ports
associated with the slat, main wing element, and/or flap to achieve
synergistic control of fluid flow over the aircraft wing to achieve
higher lift levels. FIGS. 3 and 4 illustrate that a fluidic device
18 is associated with a pair of ports in each of the wing elements.
However, the fluidic devices 18 may selectively actuate any number
of ports to realize increased gains in aerodynamic performance of
the aircraft wing. The ports are generally actuated during take-off
or landing of an aircraft, where high lift is desirable. In
addition, fluid flow through respective ports is typically
continuous during take-off and landing (i.e., constant ingestion
and ejection of fluid), although ports could be selectively
regulated during take-off and landing to achieve oscillatory fluid
flow if desired. Fluid is generally ejected through a respective
port in the general direction of fluid flow, although the fluid
could be ejected in various directions such as adjacent or
perpendicular to a respective slat, main wing element, or flap or
in a direction opposing the direction of fluid flow. Additionally,
fluid may be ingested on a lower surface of the aircraft wing and
ejected on an upper surface of the wing, ingested and ejected on
the upper or lower surfaces of the wing, or ingested on an upper
surface of the wing and ejected on a lower surface of the wing to
affect the aerodynamic performance of the wing. Moreover, the
fluidic devices may operate in conjunction with a feedback system
such that the ports may be actuated automatically. For instance,
sensors on the aircraft wing could provide information relating to
various aerodynamic properties indicative of the fluid flowing over
the wing such that particular ports may be actuated based on the
information to improve aerodynamic performance. However, the
fluidic devices may be operated manually such that the ports are
actuated when desired or at predetermined flight conditions, such
as during take-off or landing.
FIG. 5A illustrates a multi-element aircraft wing 30 including
ports defined in each of a slat 32, main wing element 34, and flap
36. The slat 32 includes ports s1-s2, the main wing element 34
includes ports m1-m3, and the flap 36 includes ports f1-f5. FIGS.
5B-5D provide graphs depicting various aerodynamic properties for
the multi-element aircraft wing 30. For purposes of simulating
take-off conditions, the slat 22 is extended, and the flap is
deflected at .delta.=24.degree..
FIG. 5B shows a lift coefficient, C.sub.L, plotted against an angle
of attack, .alpha., for inviscid flow, the viscous flow over a
baseline multi-element aircraft wing (i.e., no ports actuated), and
the viscous flow over the multi-element aircraft wing with various
ports associated with the slat 32, main wing element 34, and flap
36 actuated. The following convention is used to identify actuation
patterns: the numerals indicate the port number and minus ("m") and
plus ("p") denote ingestion and ejection, respectively. For
example, s(1m2p), m(2m3p), and f(2m3p) describe an upper surface
actuator for each of the slat 32, main wing element 34, and flap
36, where f(2m3p) designates a flap actuator having suction at port
2 and blowing at port 3.
As shown in FIG. 5B, actuating the ports in the slat 32, main wing
element 34, and/or flap 36 provides higher C.sub.L above an angle
of attack of about 9.degree. than the baseline multi-element
aircraft wing with no ports actuated. In addition, actuating ports
s(1m2p), m(2m3p), and f(2m3p) provides the greatest increase in
C.sub.LMax (.about.6.0) and results in higher than inviscid lift up
to an angle of attack of about 22.degree.. Actuating ports m(2m3p)
and f(2m3p) results in lift approximately matching the inviscid
level up to an angle of attack of about 12.degree.. FIG. 5C (drag
polar) also illustrates that actuating the ports in the slat 32,
main wing element 34, and/or flap 36 generally results in lower
drag in comparison to the baseline wing for a given lift level.
Thus, actuating ports in the multi-element aircraft wing 30 results
in an increased C.sub.L in comparison to the baseline aircraft wing
for almost the entire range of coefficient of drag (C.sub.D). As
described above, increasing C.sub.Lmax, i.e., the maximum
attainable value of C.sub.L, will decrease the stall speed thereby
facilitating shorter take-off and landing distances. Moreover,
payload capacity may be increased.
The simulations illustrated in FIGS. 5B and 5C indicate that the
aerodynamic performance can be significantly affected by the mode
of actuation. In particular, in the linear portion of the lift
curve shown in FIG. 5B, separate actuation of the ports associated
with each of the slat 32, main wing element 34, or flap 36 results
in modest improvements in aerodynamic performance. However,
combining actuation patterns in each of the slat 32, main wing
element 34, and flap 36 is most effective at reaching or exceeding
inviscid levels. Generally, achieving lift levels beyond inviscid
levels can be obtained depending on the net momentum addition
provided by the fluidic devices.
FIGS. 6A-6C illustrate lift (i.e., C.sub.L) obtained with ingestion
and ejection occurring on the upper surface of a multi-element
aircraft wing ("UTU" denotes Upper-surface-To-Upper-surface) and
ingestion on a lower surface and ejection on the upper surface of a
multi-element aircraft wing ("LTU" denotes
Lower-surface-To-Upper-surface). The UTU configuration includes
actuating three ports s(1m2p), m(2m3p), and f(2m3p), while the LTU
configuration includes actuating a set of six upper and lower ports
where blowing ports are denoted by s(1p2p), m(2p3p), and f(2p3p).
During actuation of the LTU configuration, fluidic devices ingest
air through the suction port located on the lower surface of the
wing and eject air through respective discharge port on the upper
surface of the wing. Moreover, FIGS. 6A-6C plot the UTU and LTU
configurations on the same graph as a baseline aircraft wing with
no ports actuated, inviscid flow, and oscillatory actuation (i.e.,
actuating individual ports). FIG. 6A corresponds to a take-off
configuration (flap angle .delta.=13.degree.), FIG. 6B corresponds
to another take-off configuration (.delta.=24.degree.), and FIG. 6C
corresponds to a landing configuration (.delta.=40.degree.).
FIGS. 6A-6C demonstrate that using the UTU and LTU configurations
in conjunction with constant fluid flow results in an increased
C.sub.L in comparison to the oscillatory flow control ("OFC") and
baseline configurations. Both the UTU and LTU configurations also
produce lift higher than inviscid levels for angles of attack below
about 24.degree. for .delta.=13.degree. and below about 22.degree.
for .delta.=24.degree.. Also, the OFC configuration achieved about
50-60% of C.sub.Lmax over the baseline wing in comparison to the
C.sub.Lmax of the LTU configuration. Furthermore, the LTU
configuration performed slightly better than the UTU configuration.
Utilizing an LTU configuration is desirable given its reduced power
requirements resulting from the negative upper-to-lower surface
pressure differential (i.e., from a high pressure region to a low
pressure region). The simulations illustrate that not only is
inviscid lift level achievable, but it may even be surpassed when
predetermined ports are actuated and fluid flow is constant
therethrough.
FIGS. 7A and 7B depict the total pressure field over a
multi-element aircraft wing for the baseline and flow control cases
in FIG. 6C, where the actuation is provided according to UTU
s(1m2p), m(2m3p), and f(2m3p). The images illustrate the flowfields
for the flap deflection of 40.degree. and a 16.degree. angle of
attack. The baseline case results in a C.sub.L of about 3.91 while
the actuation produces 6.14. FIG. 7A illustrates that without flow
control, the flow is not efficient, i.e., the viscous layers and
the wakes associated with the individual wing elements are quite
sizeable with large total pressure losses. In contrast, FIG. 7B
demonstrates that the actuation results in narrower viscous layers
with reduced total pressure losses and more streamlined flow over
the multi-element aircraft wing 30. As a result, a larger turning
angle is defined in the wake of the aircraft wing, which increases
lift, and flow reversal is reduced, if not eliminated. Furthermore,
FIG. 8B also illustrates a more streamlined velocity component by
actuating the ports associated with the aircraft wing. The slat
wake shown in FIG. 8B is narrower than the wake shown in FIG. 8A,
and the velocity defect is reduced. Flow reversal is also
significantly reduced, if not eliminated, in the wake of the flap
36, while lift is also increased as shown by the higher suction
level on the upper surface. As a result of the streamlined wake of
the slat 32, the flow quality on the main wing element 34 and the
flap 36 is improved, where flow reversal no longer occurs.
FIG. 9A depicts a multi-element aircraft wing 40 according to
another embodiment of the present invention. The multi-element
aircraft wing 40 includes a Krueger slat 42, a main wing element
44, and a flap 46 deflected at 50.degree.. The flap 46 is deflected
50.degree. to represent landing conditions in which flow is
separated over most of the flap even at low angles of attack.
Moreover, the slat 42 includes ports s1-s2, the main wing element
44 includes ports m1-m5, and the flap 46 includes ports f1-f5. As
before, FIG. 9B demonstrates that selectively actuating ports
m(4m5p) and f(1m2p), s(1m2p) and f(1m2p), or ports s(1m2p),
m(4m5p), and f(1m2p) results in increased C.sub.L in comparison to
both the baseline configuration (i.e., no ports actuated) and the
oscillatory actuation OFC. In general, actuating ports in each of
the wing elements of the multi-element aircraft wing 30 exceeds
inviscid levels at angles of attack less than about 24.degree. and
achieves a significantly higher C.sub.Lmax (.about.7.3) than the
baseline aircraft wing. Moreover, FIG. 9B shows that constant fluid
flow through the ports results in a greater C.sub.L than
oscillatory fluid flow (C.sub.Lmax.about.6.2). Moreover, FIGS.
9C-9D demonstrate reduced drag and increased L/D for a given lift
coefficient when the same combination of ports are actuated versus
individually actuating ports, employing oscillatory fluid flow, or
the baseline wing with no actuation. Moreover, actuating ports in
the multi-element aircraft wing 40 results in an increased C.sub.L
in comparison to the baseline aircraft wing for a given coefficient
of drag (C.sub.D).
FIG. 10 depicts a graphical illustration of C.sub.L versus angle of
attack for various configurations of ports actuated for a
multi-element aircraft wing employing a Krueger slat and flap
deflection of 50.degree.. As shown, actuating multiple ports in
each of the slat, main wing element, and flap (s(1m2m),
m(2p3p4p5p), and f(1p2p3p4p5p)) and using a LTU configuration for
the main wing element and flap and an
Upper-surface-To-Lower-surface ("UTL") configuration for the slat
results in the highest C.sub.Lmax (.about.8.7) and performs above
inviscid levels for the angles of attack up to at least about
32.degree.. Moreover, actuating a pair of ports in each of the
slat, main wing element, and flap and using either the LTU and/or
UTU configuration results in a C.sub.L above inviscid levels over
the entire linear lift range. The performance of the UTU and LTU
configurations is similar at lower angles of attack (i.e., less
than about 12.degree.), but the LTU configuration exhibits gradual
degradation in lift at higher angles of attack. This drop in lift
implies that the slat is adversely affected by the actuation of the
ports and its trailing wake is detrimental to the overall flow
quality at the main element and the flap. Reversing the flow
actuation at the slat, i.e., ingesting fluid at the upper surface
of the slat and ejecting fluid at a lower surface of the slat
results in a dramatic improvement in lift (C.sub.Lmax.about.8.0).
FIG. 10 also demonstrates that OFC is again not as effective in
increasing lift as continuously ingesting and ejecting fluid
through the ports, especially in the linear lift range.
FIG. 11A illustrates an image of the total pressure field over the
multi-element aircraft wing for the baseline configuration
(C.sub.L=4.42). In FIG. 11B, each of the ports s(1m2m),
m(2p3p4p5p), and f(1p2p3p4p5p) are actuated (producing
C.sub.L=8.44) such that the slat 42 utilizes an UTL actuation,
while the main wing element 44 and flap 46 utilize a LTU
configuration. Comparison of FIGS. 11A and 11B also demonstrate the
more streamlined flow associated with the aircraft wing 40 when
compared to the baseline multi-element aircraft wing, especially
proximate to the aft portion of the main wing element 44 and flap
46. Flow reversal is eliminated in the wake of the flap 46.
Therefore, actuating multiple ports of the aircraft wing 40 in each
of the wing elements favorably affects the viscous upper surface
layers and the wakes of the slat 42, main wing element 44, and flap
46. The flow becomes streamlined in the flap region with a high
turning angle, resulting in stronger circulation on the main wing
element 44 and flap 46 and higher lift.
FIGS. 12A-12C illustrate further details of the flow structure over
the multi-element aircraft wing 40 shown in FIG. 1B. In particular
FIGS. 12B and 12C also show the velocity vectors representing the
ingestion and ejection of fluid through the ports s(1m2m),
m(2p3p4p5p), and f(1p2p3p4p5p) in each of the slat 42, main wing
element 44, and flap 46, respectively.
Embodiments of the present invention provide several advantages. In
particular, the multi-element aircraft wing includes fluidic
devices and ports for controlling the boundary layer flow over the
wing. By locating the ports at critical locations, such as,
locations of increased pressure, flow separation, or recirculation,
on the aircraft wing and actuating particular ports at
predetermined times, the aerodynamic performance of the wing,
including lift, may be improved over a wide range of angles of
attack. Actuating the ports in the multi-element aircraft wing may
result in flow effects normally associated with flaps but with
reduced drag and improved stall characteristics. Moreover, the
application to the multi-element aircraft wing may mitigate the
viscous effects and reduce the incidence of boundary layer
separation at critical regions on the wing such that fluid flow may
surpass inviscid levels. The ports and fluidic devices may be used
to manage loading on the multi-element aircraft In addition, the
fluidic devices may employ zero net mass flow such that an external
fluid source or complex plumbing is not required.
Moreover, wing load management may be utilized to minimize induced
drag at various low speed flight conditions. For example, at
take-off and climb the system can be designed to produce a more
nearly elliptical span load distribution for lower induced drag.
Lower induced drag results in lower engine power requirements which
should reduce noise since the engine is the primary source of noise
at take-off. Also, lower induced drag leads to smaller engine size
for the twin engine class of aircraft. On the other hand, during
approach and landing the system can be utilized to produce a more
triangular load distribution for higher drag, which is desirable
for better aircraft control.
Many modifications and other embodiments of the invention set forth
herein will come to mind to one skilled in the art to which this
invention pertains having the benefit of the teachings presented in
the foregoing descriptions and the associated drawings. Therefore,
it is to be understood that the invention is not to be limited to
the specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
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